The HBO series is based on George R. R. Martin's "Song of Ice and Fire" fantasy series.
Dotrice will play Pyromancer Hallyne, chief of the Guild of Alchemists, and Dillane will play Stannis Baratheon.
Other actors who have signed on for the second season include Hannah Murray as Gilly, Liam Cunningham as Davos Seaworth, Carice van Houten as Melisandre, Gwendoline Christie as Brienne and Natalie Dormer as Margaery Tyrell.
Dotrice won the Tony Award in 2000 for his performance in A Moon for the Misbegotten. He has also been seen on Broadway in Brief Lives, Mister Lincoln, A Life, Kingdoms, Hay Fever and The Homecoming. Dillane won the Tony Award in 2000 for his performance in The Real Thing.
For more information on "Game of Thrones," click here.
